Auxiliary loud-speaker system



Feb. 20, 1968 H. w. SHAW ETAL 3,370,125

AUXILIARY LOUD-SPEAKER SYSTEM Filed May 26, 1964 INVENTORS Henry W. Show8" Howard C. Gamble ABSTRAQT OF THE DISCLOSURE An auxiliary loud speakersystem wherein multiple locally powered units can be coupled to a mainspeaker unit.

The input to each is taken from the output of the preceding unit. Aby-pass connection employing a drop-out relay enables any speaker unitto be turned off or to malfunction with no effect upon those that followit and further enables the entire system to be turned off from the mainspeaker unit.

This invention relates to a system utilizing auxiliary loud speakerunits which are powered and connected to a powered main soundreproducing unit such as a portable lectern for speakers at indoorand/or outdoor exercises. More particularly, this invention pertains tosuch a system in which any desired number of units may be added to amain unit and each other to accommodate audiences of different sizesand/or auditoriums or fields, so that the person speaking or othersound, such as music, for example, may be heard clearly withoutdistortion, differences in phasing between the respective auxiliaryloudspeaker units, and at comfortable volume levels throughout the soundbroadcast area.

One common practice heretofore in the use of a public address system forspeech or other sound, whether portable or fixed, involved the use of asingle main unit usually with a high powered amplifier so that if alarger audience were present the volume control could be turned up toincrease the output resulting, however, in overloudness for auditorsnearer the main unit and a tendency to distortion. On the other hand,when additional loud speakers were connected to the audio output of themain unit, problems arose in matters of energy distribution to thesupplemental speakers, line losses, impedance matching, and, phasing ofthe supplemental speakers relative to the output of any speaker in themain unit. While such problems could be taken care of beforehand in apublic address system with relatively previously predeterminedcomponents including supplemental loud-speakers, the use of supplementalspeakers in varying numbers at varying distances under varyingcircumstances, deriving their power from a main unit, whether portableor fixed, resulted in such problems remaining relatively unsolved, evenwhen last minute adjustments were attempted.

In a powered auxiliary loud-speaker system of this invention, suchshortcomings and deficiencies are overcome whether the main unit andauxiliary loud speakers are portable, or fixed, in Whole or in part.Under this invention, any selected number of powered auxiliary loudspeaker units may be added to the main unit, within the capacity of thesystem, to reach audiences of any size even as determined at the lastmoment without requiring computation and adjustment to compensate forproblems of line loss, impedance matching, speaker phasing, or otherdistorting factors. For example, a portable powered lectern such as thatillustrated in Patent No. 3,023,274, in common ownership with thisinvention, may be used conveniently to address an audience of from 50 to1000 people. The addition of powered auxiliary loud speakers of thisinvention may be done quickly and conviently simply by plugging theminto the main unit and/or one States Patent another in serial and/ orparallel arrangement, as may be desired, to reach audiences of up to20,000 people and over, even in the open air, without distress of thosein the audience nearer the main unit, or loss of quality and clarity ofsound to those on the fringes of the group. Under this invention, eachpowered auxiliary loud speaker is self-contained and normally providesits own power; in case of failure of power in a particular auxiliaryunit, it is arranged in such wise that it does not cut off thoseauxiliary units which are farther away and connected through it to themain unit. On the other hand, when the amplified sound output is shutoff at the main unit, the entire system will become silent.

Other objects, features and advantages of this invention will beapparent from the following description and the accompanying drawings,which are illustrative of one embodiment only, in which FIGURE 1 is aschematic view of one embodiment of this invention with poweredauxiliary loud-speakers in series connection to a main unit;

FIGURE 2 is a perspective view of two powered auxiliary units which whenfastened together comprise a single carrying set;

FIGURE 3 is a view of the two auxiliary speaker units shown in FIGURE 2after they have been fastened together and are ready for such carrying;and

FIGURE 4 is a circuit diagram of one powered auxiliary speaker unit forpurposes of illustrating one mode of functioning of the system of thisinvention.

Referring to the drawings, a portable powered lectern 10 comprising amain unit is shown in opened operative condition for a person to speakinto a microphone 11 connected to a suitable transducer-amplifier inlectern 10 to actuate one or more loud-speakers located in the lecternbehind a cloth screen or grill 12 so as to face an audience. Microphone11 is mounted on a boom arm adjacent a lectern surface 13 on which thespeaker may place his notes or other material for the talk to be given.While main unit 10 is illustrated in the form of a powered speakerslectern which is portable, it will be understood that it may be fixed;it may be understood, further that such main unit 10 may comprise otherkinds of main units with an audio output circuit for the transmission ofreproduced and amplified sound audible to human beings. Or, such mainunit 10 may provide an amplified audio signal output at some remotelocation, for example, to supply powered auxiliary loudspeakers. In theillustrated embodiment of this invention using lectern 10, a string ofsuch self-contained powered auxiliary speaker units is represented byidentical auxiliary units bearing numerals 14 to 17, inclusive andrespectively, to be placed at spaced intervals among the audience.Further, although auxiliary speakers 14 to 17, inclusive, areillustrated in series connection beginning at output panel 18 on mainunit 10, forming an extended trunk of such auxiliary speakers, eitherthe main unit 10, or any of the auxiliary speakers may have parallelbranches of auxiliary speakers leading therefrom in a tree and brancharrangement, if desired, by the use of sockets, plugs or adapters whichallow more than one of such auxiliary speakers to be connected to apowered main or auxiliary speaker unit, to cover any arrangement of anaudience, whether fanshaped, columnar, or bent as in the case of ameeting hall having bays to each side in which an embodiment of thisinvention is used.

As shown, each powered auxiliary speaker unit of this invention is in acase 19 the back of which is an open recess and extends inwardly to apartition 20 having a volume control 21, a switch 22 and an outputsocket 23 mounted on the partition and facing rearwardly. A long lengthof lamp cord 24 connects each of the auxiliary speakers to animmediately preceding unit; when not in use, such lamp cord 24 may becoiled and fitted into the aforesaid recess of its unit where it may beheld by a strap or clip secured to partition 20. The front side of eachauxiliary speaker may be provided with a combination fabric and grillscreen 25 overlying one or more auxiliary speaker horns 26. In theauxiliary speaker units shown in the illustrated embodiment, threerelatively uniform diameter horns are arranged in a vertical columnbetween partition 20 and screen 25 together with most of the circuitcomponents shown in FIGURE 4. At the bottom of the aforesaid recess inthe back of each speaker unit may be positioned dry cell batteries 27for the amplifier therein. If desired, a battery meter may also bemounted on panel 20 to shown when such batteries have to be replaced.

Each case 19 is provided with four cushion feet 28 at the corners andalong the bottom rear edge there is a spaced pair of the same leaf of apair of separable hinges 29. Thereby, when two cases 19 having oppositehinge leaves thereon are placed back-to-back, a carrying set 195 isformed comprising a pair of auxiliary speaker units, as shown in FIGURE4. The upper rear edge of each case 19 in a set is attached to anappropriate half of a separable toggle clasp 30, which is closed tocomplete the fastening together of two cases 19 hinged to each other toform set 198. Each case 19 also has a half handle 31 so that when twocases are formed into a set, both such half handles form a full diametercarrying handle as illustrated in FIGURE 3. Since each auxiliary speakerunit is powered, although such may be used in a series arrangement withan alternately positioned unpowered auxiliary speaker on some occasions,no ditficulty is encountered in quickly setting up to address anaudience of virtually any size, either under a roof, or in the open air.The rest of the cord 24, which may be fifty feet long or more, for eachauxiliary unit, enables them to be placed where they best will serve andthey may 'be faced in any direction relative to the main unit and theother auxiliary units, depending upon the location of the audience, andany wind conditions or other factors that have to be taken into accountat the time of setting up. All of the powered auxiliary speakers of thisinvention are connected in proper polarity so that the sound uttered bythem at a given instant will be the same and also the same as the sounduttered by the main unit. Moreover, the power output of the main unit isnot relied upon to reach part of a larger audience beyond the normal andintended number within the capacity of that main unit inasmuch as eachof the auxiliary loud-speaker units in a system of this invention takescare of its own sound reproduction and amplification by means of its ownamplifier, thereby eliminating need for concern about impedance matchingrelative to the main unit, auxiliary unit and lines losses between unitsand other distortion elements. Still further, if an amplifier in one ofthe powered auxiliary speaker units of this invention should fail, itwill not cut out or adversely effect other such units which may befarther out or away from the main unit. At the same time, when the mainunit is shut off it will automatically silence the auxiliary speakerunits and open the respective battery circuits in them. Although thedescription herein has to do with a portable auxiliary loudspeakersystem to be used with a main speaker or audio sound output signal unit,it will be recognized that systems which are permanently fixed in place,or semi-permanently fixed in place, may be provided which embodyteachings of this invention.

In operation, when the main unit is turned on, an electrical switch 52is closed and the circuit in unit 10 is energized to produce anamplified output audio signal across the secondary 50 of an output audiotransformer therein. Such drives the speaker or speakers 51 in unit 10and imposes such audio signal across the polarity terminals 53 and 54 ofa receptacle socket 55 mounted on or adjacent the surface of unit 10 ina position accessible from the outside. Socket 55 is adapted to bebridged by the respective prong terminals 56 and 57 of a polarity plug58 at the far end of a cord 24 leading to a powered auxiliary speaker ofa system of this invention, which in the illustrated embodiment isspeaker 14. Because of the respectively different sizes of the prongterminals of socket 55 and plug 58, there can be no reversal of polarityin the feeding of the audio signal to the next succeeding unit and suchpolarity oriented socket and plug connection continue in each succeedingconnection. Jacktype plugs and sockets may also be used.

In auxiliary speaker unit 14, the closing of On-Off" switch 22 and theinsertion of plug 58 into socket 55 energizes a relay 59 by means ofbatteries 27 for D.C. current flow through a portion of the audio outputcircuit of the preceding unit via conductor 60, coupled terminal 57-54,coil 50, closed switch 52 to the coupled terminal 55-56, a blockingcondenser 61 preventing D.C. current from passing through the speaker51; thence back through On switch 22 to the battery in unit 14, or otherauxiliary unit as the case might be. Such energization of relay 59closes a normally open gang switch 62, raising its three movable switcharms into contact with their respective, closedposition terminals towhich such switch arms are shown extending in full line position inFIGURE 4. As a consequence, the wave form of the audio input signal isimpressed across a potentiometer resistance 63 through the middle gangswitch arm, such resistance with a selector element 64 comprising volumecontrol 21 and feeding the primary side of an input transformer 65 in atransistorized push-pull amplifier 66. The D.C. supply for thetransistors 67 and 68 is supplied by D.C. current from the battery 27flowing through a subcircuit completed by the uppermost switch arm ofgang switch 62, through resistances 69 and 70 and conductor 71. Hence,the impressed audio signal through the secondary of transformer 65respectively modulates the flow of current through the respectivetransistors 67 and 68 to supply an amplified audio signal to the primary72 of amplifier output audio trans former 73, thereby embodying withinthe powered auxiliary speaker selected amplification in situ for thatportion of the audience comfortably and conveniently reached by itsspeakers 26.

The amplified audio output subcircuit of the auxiliary speaker 14 whosefull circuit is shown in FIGURE 4, is completed by the raising of thelowermost switch arm 76 of gang switch 62 to the full line positionshown in FIG- URE 4, thereby placing the secondary 74 of transformer 73in a subcircuit which proceeds through conductor 75, switch arm 76,conductor 77, the switch arm of switch 22 in its On" position, speakers26 and conductor 78 back to the other side of secondary 74. A capacitor79 blocks off any D.C. current to the speakers 26. Aresistance-capacitor feedback connection 74a is provided between thesecondary of the output transformer 73 and an earlier stage of audioamplifier 66 to inhibit distortion of the output audio signal from suchauxiliary unit.

A branch subscript across secondary coil 74 leads to the respectivepolarity terminals 80 and 81 of socket 23, adapted, when needed, to beengaged in one position only by a plug 82 of the next succeedingspeaker, such as speaker 15; plug 82 being identical to plug 58 andconnected by a lamp cord 83 identical to lamp cord 24, just as thecircuit in powered auxiliary speaker 15 is identical, for theillustrated embodiment, to the circuit of speaker 14 shown in FIGURE 4.When plug 82 is inserted in socket 23, the battery circuit of speaker 15for the actuation of its relay corresponding to relay 59, is completedby the audio output portion of the circuit of speaker 14. Thus, uponsuch insertion, current flows from one terminal in socket 23 throughclosed (On) arm of switch 22, conductor 77, raised switch arm 76,conductor 75, the coil 74 and conductor 78 to the other terminal ofsocket 23. It is clear also that When switch 62 is opened by turning offmain unit 10, all of the powered auxiliary loudspeaker units of thisinvention will fall silent inasmuch as the gang switches in each of themwill drop out automatically by virtue of the deenergization of relay 59and those corresponding thereto in the other speakers, namely, 15 to 17in the illustrated embodiment.

Further, in the event that in one of the auxiliary speakers, such asspeaker 14, battery 27 should become too weak to energize relay 59sufiiciently to hold gang switch 62 in closed (raised) position, thegang switch will drop out shutting off the amplifier 66 in that speaker.A lamp circuit may be installed, if desired, to show any dropping out ofgang switch 62 when switch 22 is still in its On position; or a batterymeter may be mounted on partition 20 to indicate when the battery dropsso much in strength as to be unable to energize the relay sufiicientlyto hold the gang switch in operative position to provide auxiliaryamplification therein. When gang switch 62 opens due to insufiicientbattery strength, the uppermost switch arm will fall down into contactwith rest 84, the middle switch arm will move downwardly into engagementwith terminal 85 and the lowermost switch arm will move downwardly intoengagement with terminal 86. Terminals 85 and 86 are connected by a lead87 with the consequence that the audio signal impressed across theterminals of plug 58 will be impressed across the terminals of socket 23in correct polarity relation without, however, amplification thereof inunit 14. Speakers 26 will receive energy at the level supplied by mainunit 10, or a prior auxiliary speaker unit if the one cutting outfollows an earlier auxiliary unit in the string leading back tothe mainunit. The unamplified audio signal thus received across the terminals ofplug 58 will be conducted through the one side of cord 24, switch-22,conductor 88, the middle contact movable arm of gang switch 62, jumper87, the lowermost movable arm of switch '62, conductor 77, the movablearm of switch 22 to terminal 80 of socket 23. Such audio signal willthen pass through the still completed audio input portion of the circuitin the next succeeding auxiliary speaker leading to terminal 81,terminal 81 and from thence through conductors 78, 71 and 60, back toterminal 57 of plug 58. Or, if switch 22 of one of the auxiliaryspeakers such as speaker 14 should be turned Off, .the audio inputsignal impressed across the terminals of the input plug 58, or identicalinput plug of any other of such auxiliary speakers, will then passwithout amplification through the movable arm of switch 22 in Offposition leading to one terminal of socket 23, a jumper 89 shown in thecircuit diagram being shown simply for ease of illustration, since the01f position of switch 22 in the two positions shown in the circuitdiagram may be one and the same. The other terminal on the output socket23 completes the subcircuit to such terminals of socket 23 throughconductors 78, '71 and 60 to the corresponding input plug terminal 57.Hence, when switch 22 is turned Off while a powered auxiliary speaker ofthis invention is in connection with the main unit or the main unit andother powered auxiliary speakers of this invention, while there will beno amplification in that turned-off auxiliary speaker, it will bypassthe audio signal to the next succeeding unit and the speaker means 26 ofthe turned off auxiliary speaker will receive signal impulses at theenergy level of the immediately preceding unit turned-on unit when themain unit is On, which may be suflicient for some operation thereof suchspeaker means 26 at lowered volume. Or, turning switch 22 to Ofiposition may be used to cut-off any amplification in that unit and anybypassing of the audio signal to a succeeding unit, by a single circuitchange breaking conductor 60 when switch 22 is Off.

From the foregoing, it will also be clear that the auxiliaryloud-speaker system of this invention may be readily set up and asquickly taken down for the service of audiences of any size, even ifsuch is determined at a late moment. And, the illustrated embodiment iswholly portable, or may be fixed, inasmuch as each pair of auxiliaryspeaker units can be quickly fastened together into a set forconvenience in carrying as portrayed in FIGURE 3, either to storage, formovement to the next place of use. And in some situations, rectifiedcurrent may be used as a DC. source in powered auxiliary unit.

Various changes may be made in details and circuit portions of theillustrated powered auxiliary speaker embodiment and other embodimentsprovided without departing from the spirit of this invention or thescope of the appended claims.

What is claimed is:

1. An auxiliary loud-speaker unit comprising an amplifying circuithaving polarized audio input means and polarized output means, at leastone loud-speaker coupled across said audio output means, a supplycircuit for supplying energizing otential to said amplifying circuit, acircuit path connecting said input means and said output means inpolarized relation, said circuit path by-passing said amplifyingcircuit, and switch means in said by-passing circuit path and in saidsupply circuit for completing said by-passing circuit only when saidsupply circuit is disconnected from said amplifying circuit.

2. The combination according to claim 1 wherein switch means include arelay switch having a coil energizable by said supply circuit, saidrelay switch having normally closed contact means coupled to said inputand said output means in by-passing relation to said amplifying circuitand having normally open contact means in said supply circuit. 7

3. In an auxiliary loud-speaker system, the combination comprising aplurality of self-powered auxiliary speaker units, each auxiliary unithaving audio input means and audio output means, circuit means forcoupling said input means to the output of a similar adjacent unit andfor coupling said output means to the input of a different adjacentunit, each of said auxiliary units including a local audio amplifyingcircuit, circuit means for coupling said amplifying circuit to theassociated input means and output means and to a source of energizingpotential therefor, each of said auxiliary units having at least oneloud-speaker coupled across'its audio output means, and switching meansin each of said auxiliary units for directly interconnecting the inputmeans and output means thereof in by-passing relation to the amplifyingcircuit when the latter is de-energized so that said adjacent unitsremain electrically interconnected through said de-energized unit.

4. The combination according to claim 3 wherein switch means are inseries with said main unit output means for controlling the audioenergization of said main unit output means and for simultaneouslycontrolling the audio energization of said auxiliary units.

5. In an auxiliary loud-speaker system in combination, a main loudspeaker unit having audio signal output means, polarized main unitoutput terminals connected in parallel with said output means, an on-olfswitch in the circuit of said main unit terminals, a loud-speaker insaid main unit connected across said output means, at least one locallypowered auxiliary speaker unit having audio signal input means includingpolarized input terminals connectable with said m'ain unit outputterminals, said auxiliary unit further having an audio signal amplifyingcircuit therein connected to said signal input means, said amplifyingcircuit including a transistorized push-pull amplifier coupled to anaudio output transformer and to local audio signal output meansincluding polarized output terminals for connection to similarlypolarized audio input terminals of another auxiliary speaker unit, saidfirst-mentioned auxiliary unit having at least one loud-speakerconnected across the secondary of said audio transformer, a local sourceof DC. potential coupled to said amplifying circuit through a relayswitch having a coil connected to said source for energization thereby,said relay switch having normally open contacts coupling said source andsaid auxiliary unit speaker to said amplifying circuit and normallyclosed contacts coupled in circuit means connecting the input and outputterminals of said auxiliary unit in by-passing relation to itsamplifying circuit, manually operable switch means having first contactmeans for coupling the coil of said relay switch to said source andalternative second contact means for coupling said auxiliary unit outputterminals in polarized relation to the input terminals thereof and inby-passing relation to said amplifying circuit when said relay switchcoil is de-energized.

6. In an auxiliary loud-speaker system, in combination, a first speakerunit having audio signal output means, polarized audio output terminalsconnected across said output means, at least one loud-speaker in saidfirst unit connected across said output means, at least one auxiliaryspeaker unit having similarly polarized audio input terminals, means forelectrically connecting said input and said output terminals, an audiosignal amplifying circuit in said auxiliary unit coupled to said inputterminals, a supply circuit in said auxiliary unit for connecting saidamplifying circuit to a source of DC. potential, a relay switch in saidsupply circuit having a coil energizable by said source, said amplifyingcircuit including an audio output transformer, said auxiliary unithaving at least one loud-speaker and polarized output terminal meansconnected across the secondary of said output transformer, said relayswitch having normally open contacts coupling said DC. source and saidauxiliary unit speaker to said amplifying circuit and normally closedcontacts by-passing said amplifying circuit when said relay switch coilis de-energized, and manually operable switch means having first contactmeans in series with the coil of said relay switch and alternativesecond contact means for coupling said auxiliary unit output terminalsin polarized relation to the input terminals thereof and in by-passingrelation to said amplifying circuit.

7. In an auxiliary loud-speaker system, in combination, a first unithaving audio signal output means and polarized terminals connectedthereacross, at least one auxiliary speaker unit having audio signalinput means and polarized terminals connected thereacross, means forconnecting the input terminals of said auxiliary unit to the outputterminals of said first unit, an audio signal amplifying circuit in saidauxiliary unit coupled to said audio signal input means, a supplycircuit for coupling said amplifying circuit to a source of electricpotential,

said amplifying circuit having audio signal output means, said auxiliaryunit having at least one loud-speaker and polarized output terminalsconnected across said audio signal output means associated with saidamplifying circuit, means for connecting the output terminals of saidauxiliary unit to polarized input terminals of a similar auxiliary unit,and switch means on said auxiliary unit having first contact means inseries with said supply circuit and alternative second contact means forcoupling said auxiliary unit output terminals in polarized relation tothe input terminals thereof and in by-passing relation to saidamplifying circuit so that upon de-energizing of said amplifying circuitsecond contact means couple said similar auxiliary unit in polarizedrelation to said first unit through said auxiliary unit.

8. In an auxiliary loud-speaker system having a main speaker unit, thecombination comprising a plurality of self-contained power auxiliaryspeaker units coupled to said main speaker unit, each of said auxiliaryspeaker units having an audio amplifying circuit therein including audiosignal input means coupled to audio signal output means of an adjacentone of said units, the amplifying circuit of each of said auxiliaryunits having audio output means, at least one loud-speaker connectedacross each of said amplifying circuit output means, each of saidauxiliary units including a supply circuit for supplying a DC. potentialto the associated amplifying circuit and to the coil of a relay switch,said relay switch having normally open contacts coupling said supplycircuit and said auxiliary unit speaker and said auxiliary unit outputmeans to said amplifying circuit, said relay switch having normallyclosed contacts coupling said auxiliary unit audio signal input meansdirectly to the audio signal output means of said auxiliary unit inbypassing relation to the amplifying circuit thereof, and manuallyoperable switch means having first contact means for coupling said relayswitch coil to said supply circuit and alternative second contact meansfor coupling said auxiliary unit input means to the output means thereofin by-passing relation to the amplifying circuit thereof.

References Cited UNITED STATES PATENTS 3,023,274 2/1962 Shaw 179--13,167,314 1/1965 Bentsen. 181-3 1.1 3,183,305 5/1965 Jespersen 179lKATHLEEN H. CLAFFY, Primary Examiner.

R. P. TAYLOR, Alrsistant Examiner.

